Ranger animal companions

[KoDT69]

I have a custom Ranger that basically gets the Horizon Walker abilities added free at every even level. He is a level 6 now, and still running with a regular hunting dog. What is the best animal he could attract? I was thinking of giving him a chance to tame something like a Hellhound or an elite array Blink-Dog that can speak common or Elvish. Would those even be worth it?

[Pluto!]

I have a custom Ranger that basically gets the Horizon Walker abilities added free at every even level. He is a level 6 now, and still running with a regular hunting dog. What is the best animal he could attract? I was thinking of giving him a chance to tame something like a Hellhound or an elite array Blink-Dog that can speak common or Elvish. Would those even be worth it?
What do you mean "worth it"?

There aren't specified paths for getting Hellhounds or Blinkdog companions, so I'm not sure what the tradeoff would be - a session spent on a side quest? Sure, why not. But if the trade off involves something like blowing four feat slots, then probably not.

[Urpriest]

It would be kind of strange for the character to branch out from animals unless they had an appropriate theme.

[Biffoniacus_Furiou]

You seem to be missing the point of animal companions. A Blink Dog is a magical beast, a Hellhound is an outsider. Only animals are eligible to become an animal companion, though there are a few very specific exceptions. For example, you would need to take the Exalted Companion feat in BoED to get a Blink Dog. There's currently not a way to get a Hellhound as an animal companion, but it's available as a familiar via Improved Familiar in CW.

If you want a stronger animal companion, you should take the Natural Bond feat in Complete Adventurer, which adds +3 to your effective druid level for your animal companion class feature. Get one of the stronger animals available, such as a Fleshraker dinosaur from MM3 (Level -3) or a Dire Eagle in RoS (Level -3). Use Handle Animal and take some time training it to give it the Warbeast template in MM2.

Consider picking up Wild Cohort (http://archive.wizards.com/default.asp?x=dnd/re/20031118a) if you can recruit a new companion that benefits from both this and your Animal Companion class feature. You would need to be 7th level to get a 'Level -3' creature as a wild cohort, but it would only be down by three levels for that progression. So your companion would get more HD and more bonuses to ability scores and natural armor, and actually be able to make a significant contribution.